I really like the one I have from Nashbar: Nashbar Frame Pack Bag - Normal Shipping Ground
Works good for a few tools and spare tube.


It is a good alternative to a seat bag. Any reason why you want a frame bag rather than an under the seat bag?


I also have one of these for times when I have to carry stuff but don’t want panniers (very well designed and made bag:
Revelate Designs Tangle Frame Pack | Bike Bag


And J&D makes a good (more basic, less expensive) alternative.
Frame Pack


Another option:
Frame Pack, Medium | Banjo Brothers